Fuel container and delivery apparatus for a liquid feed fuel cell system

ABSTRACT

A fuel container and delivery apparatus is provided which also allows for removal of effluents from the fuel cell. The fuel container and delivery assembly includes an inner flexible bladder containing fuel for a liquid feed fuel cell. The fuel container and delivery assembly is fitted with a pressure-applying element that exerts a continuous pressure upon the fuel-containing flexible bladder in such a manner that the fuel is expressed through a conduit in the container to the direct oxidation fuel cell. The fuel is supplied to the fuel cell in a continuous manner, or on demand. The fuel container may be a replaceable cartridge. In accordance with one embodiment of the invention, the assembly includes a second bladder that is provided to receive effluent from the fuel cell which may be comprised of carbon dioxide and unreacted fuel and water from the anode side, or of water from the cathode side, or a combination of both.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation-in-part of commonly assignedU.S. patent application Ser. No. 10/041,301, filed Jan. 8, 2002, nowU.S. Pat. No. 7,074,511, which issued on Jul. 11, 2006 to Becerra, etal, for a FUEL CONTAINER AND DELIVERY APPARATUS FOR A LIQUID FEED FUELCELL SYSTEM and is hereby incorporated herein by reference.

This application is a divisional of U.S. application Ser. No.10/675,668, filed Sep. 30, 2003, now U.S. Pat. No. 7,270,907, whichissued on Sep. 18, 2007, to Becerra, et al., and is hereby incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of liquid feed fuelcells, including direct oxidation fuel cells and, more particularly, toa fuel container and delivery apparatus for systems including such fuelcells.

2. Background Information

Fuel cells are devices in which an electrochemical reaction is used togenerate electricity. A variety of materials may be suited for use as afuel depending upon the materials chosen for the components of the cell.Organic materials, such as methanol or natural gas, are attractivechoices for fuel due to the their high specific energy. Liquid feed fuelcells employ a liquid substance, such as methanol, as the fuel.

By way of background, fuel cell systems may be divided into“reformer-based” systems (i.e., those in which the fuel is processed insome fashion to extract hydrogen from the fuel before it is introducedinto the fuel cell) or “direct oxidation” systems in which the fuel isfed directly into the cell without the need for separate internalprocessing. Most currently available fuel cells are reformer-based fuelcell systems. However, because fuel-processing is technically complex,difficult and requires significant volume, reformer based systems arepresently limited to comparatively high power applications.

It should be understood that the fuel used in the cell may be either acarbonaceous liquid or a gas. A fuel cell that utilizes a liquid fuel issaid to be a “liquid feed” fuel cell. A liquid feed fuel cell may befurther categorized as a “liquid feed reformer-based fuel cell” or a“liquid feed direct oxidation fuel cell”. In some instances, it may bedesirable to store and utilize a liquid fuel, rather than a gaseousfuel, due to the ease of handling and storage of liquids, andcomparative stability of a liquid under a wide range of environmentalconditions. It should also be understood that this description isrelated primarily to liquid feed fuel cell systems, and as such thesystems are categorized simply as direct oxidation or reformer-basedsystems.

In lower power operations, such as hand held portable electronics, itmay be advantageous to utilize a direct oxidation fuel cell system. Morespecifically, direct oxidation fuel cell systems may be best suited fora number of applications in smaller mobile devices (e.g., mobile phones,handheld and laptop computers), as well as in some larger applications.

Briefly, in direct oxidation fuel cells, a carbonaceous liquid fuel(typically in an aqueous solution such as an aqueous methanol solution)is introduced to the anode face of a membrane electrode assembly (MEA).The MEA contains a protonically-conductive but, electronicallynon-conductive membrane (PCM). Typically, a catalyst, such as platinumor a platinum/ruthenium alloy, which enables direct oxidation of thefuel on the anode is disposed on the surface of the PCM (or is otherwisepresent in the anode chamber of the fuel cell). Protons (from hydrogenfound in the fuel and water molecules found on the anodic face of thereaction) are separated from the electrons. The protons migrate throughthe PCM, which is impermeable to the electrons. The electrons thus seeka different path to reunite with the protons and oxygen moleculesinvolved in the cathodic reaction. Accordingly, the electrons travelthrough a load, providing electrical power.

One example of a liquid feed fuel cell system is a direct oxidation fuelcell system, and more specifically, a direct methanol fuel cell system(or “DMFC” system). In a DMFC system, methanol in an aqueous solution isused as the liquid fuel (the “fuel mixture”), and oxygen, preferablyfrom ambient air, is used as the oxidizing agent. There are twofundamental reactions that occur in a DMFC which allow a DMFC system toprovide electricity to power-consuming devices: the anodicdisassociation of the methanol and water fuel mixture into CO₂, protons,and electrons; and the cathodic combination of protons, electrons andoxygen into water.

In order for these reactions to proceed continuously, fuel cells,including liquid feed fuel cells, must be supplied with sufficient fuelto ensure power generation. Moreover, if such a liquid feed fuel cell isto be used with a portable, handheld device, it ideally should operate,effectively, in a variety of orientations. Accordingly, a DMFC, whenused in a portable electronic device should include a fuel deliverysystem that delivers liquid fuel on either a continuous basis or upondemand, regardless of the orientation of the DMFC system.

Due to the nature of methanol, and its associated risks to persons andproperties, safety precautions are typically followed when using thissubstance. It is thus desirable to store and deliver methanol in amanner that substantially prevents leakage of the fuel from thecontainer. Furthermore, the fuel substance may be mixed with one or moreadditives that increase its detectability in case it does escape fromits container. These safety enhancing additives allow for safer handlingof the fuel substance by providing an odor and/or color to increase thelikelihood of detection of the substance, by a person who may come incontact with it if amounts of methanol are released from the fuel cell,either upon disposal or accidental breakage.

For best results, the safety-enhancing additives should be stored andmaintained separately from the fuel while the fuel is in use poweringthe relevant device. In addition to safety enhancing additives, thereare effluent substances that are produced in the fuel cell reactionsthat may or may not be useful. For example, on the anode aspect of thefuel cell, carbon dioxide is a product of the reaction, and there mayalso be excess or un-reacted fuel, water, and other products of thereaction or substances present. On the cathode side, water is produced,which may be removed, and additionally, other substances or contaminantsmay also be present that are desired to be removed. It may be desirableto remove some of these substances in a convenient manner.

The device should also conform to a small form factor and theseadvantages should be provided at an expense level that allows massmanufacturing techniques to remain feasible. Accordingly, it is anobject of the invention to provide a storage container and deliverysystem that feeds liquid fuel to a fuel cell in a continuous, orperiodic manner, but without unexpected interruption even while thedevice (being powered by the fuel cell) is operated in a variety oforientations, and which removes unwanted effluent from the fuel cell.

SUMMARY OF THE INVENTION

These and other advantages are provided by the present invention inwhich a fuel container and delivery assembly includes an inner flexiblebladder containing fuel for a liquid feed fuel cell. The fuel containerand delivery assembly is fitted with a pressure-applying element thatexerts a continuous pressure upon the fuel-containing flexible bladderin such a manner that the fuel is expressed through a conduit in thecontainer to the direct oxidation fuel cell. The fuel is supplied to thefuel cell in a continuous manner, or on demand. The fuel container maybe a replaceable cartridge. The fuel container and delivery system ofthe present invention delivers fuel simply and inexpensively to theliquid feed fuel cell while it is being used in any orientation.

In one embodiment of the invention, the pressure-applying elementincludes a spring-loaded plate or other device that compresses theflexible bladder to apply pressure to the liquid fuel in such a mannerthat it is continuously available to the fuel cell. In accordance withanother aspect of the invention, an expandable material such asexpandable foam is applied to a plate to exert pressure upon theflexible bladder.

The pressure assembly may be housed within an outer container thatdefines a plenum within which safety-enhancing additives are contained.In the event that the fuel delivery assembly is compromised or whenbeing discarded, the safety enhancing additives are mixed with the fuelto cause it to be detectable.

In yet a further embodiment of the invention, an additional internalflexible bladder is provided as a convenient way to remove unwantedeffluent from the fuel cell system, which effluent may otherwise havebeen difficult to eliminate.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention description below refers to the accompanying drawings, ofwhich:

FIG. 1 is a block diagram of a direct methanol fuel cell system withwhich the present invention may be employed;

FIG. 2 is a schematic cross section of an embodiment of the fuelcontainer and delivery assembly of the present invention in which thepressure-applying element is a spring;

FIG. 3 is a schematic cross section of one embodiment of the fuelcontainer and delivery assembly of the present invention in which thepressure-applying element is an expandable material;

FIG. 4 is a block diagram of a direct methanol fuel cell system similarto that shown in FIG. 1 which also includes a metering valve to controlthe flow of fuel into the DMFC;

FIG. 5A is a schematic cross section of an embodiment of the fuelcontainer and delivery assembly of the present invention, which has afunnel shape;

FIG. 5B is a schematic cross section of the embodiment of FIG. 5A inwhich the fuel container and delivery assembly includes a bellows typeflexible bladder;

FIG. 6 is a schematic illustration of one embodiment of the fuelcontainer and delivery assembly of the present invention that includes afuel gauge;

FIG. 7 is a schematic cross section of one embodiment of the fuelcontainer and delivery assembly that includes axially placedpressure-applying elements;

FIG. 8A is a schematic cross section of one embodiment of the fuelcontainer and delivery assembly that includes a constant force springand displacement sub-assembly;

FIG. 8B is a top plan view of the device of FIG. 8A;

FIG. 9 is a top plan view of one embodiment of a pressure-applyingelement in accordance with the invention, including a locking system;

FIG. 10A is a top plan section of a fuel cartridge of one embodiment ofthe invention having tracks upon which a fuel bladder and associatedroller can travel as fuel is consumed;

FIG. 10B is a schematic top plan view of the fuel bladder and rollerassembly that travels along the track illustrated in FIG. 10A;

FIG. 10C is a side section of one embodiment of the fuel container anddelivery assembly of the present invention wherein the pressure-applyingelement is a coil spring;

FIG. 10D is a schematic side section of a toothed track as used in theassembly of FIG. 10B;

FIG. 11 is a schematic cross section of one embodiment of the fuelcontainer and delivery assembly of the present invention incorporating adisposable fuel cartridge having a fuel recirculation feature;

FIG. 12 is a schematic cross section of one embodiment of the fuelcontainer and delivery assembly in which a dual bladder sub-assemblyprovides a high concentration fuel and a low concentration fuel; and

FIG. 13 is a schematic cross section of one embodiment of the fuelcontainer and delivery assembly in which a dual bladder sub-assemblyprovide an outlet for products of the reactions, and other substances.

DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT

The present invention is a fuel storage container and delivery assembly.The fuel may be any liquid carbonaceous fuel including, but not limitedto, methanol, ethanol, propane and butane, or aqueous solutions thereof.For purposes of illustration, we herein describe an illustrativeembodiment of the invention as it is employed in connection with adirect methanol fuel cell system (“DMFC”), with the fuel substance beingmethanol or an aqueous methanol solution. It should be understood,however, that it is within the scope of the present invention that thefuel container and delivery system can be readily used for other fuelsto be stored and delivered to direct oxidation fuel cells. Thus, as usedherein, the word “fuel” shall include methanol, ethanol, propane, butaneor combinations thereof, and aqueous solutions thereof and other liquidcarbonaceous fuels amenable to use in a direct oxidation fuel cellsystem.

For a better understanding of the invention, a direct methanol fuel cellsystem with which the invention may be employed will be brieflydescribed. FIG. 1 illustrates a direct methanol fuel system 2 with whichthe fuel container and delivery system of the present invention may beused. The system 2, including the DMFC 3, has a fuel delivery system todeliver fuel from fuel container and delivery assembly 4 in accordancewith the invention. The DMFC 3 includes a housing 5 that encloses amembrane electrode assembly 6 (MEA). MEA 6 incorporates protonicallyconductive, electronically non-conductive membrane 7 (PCM). PCM 7 has ananode face 8 and cathode face 10, each of which may be coated with acatalyst, including but not limited to platinum or a platinum/rutheniumalloy. The portion of DMFC 3 defined by the housing 5 and the anode faceof the PCM is referred to herein as the anode chamber 18. The portion ofDMFC 3 defined by the housing 5 and the cathode face of the PCM isreferred to herein as the cathode chamber 20. Additional elements of thedirect methanol fuel cell system such as flow field plates, anddiffusion layers (not shown in FIG. 1) to manage reactants andbyproducts may be included within anode chamber 18 and cathode chamber20.

Methanol or a solution of methanol and water are introduced into theanode chamber 18 of the DMFC 3, or into an internal fuel reservoir (notshown) from which the fuel solution will be delivered to the anodechamber 18. More specifically, as will be understood by those skilled inthe art, electricity-generating reactions occur when a fuel substance isintroduced to the anode face 8 of the PCM, and oxygen, typically in theform of ambient air, is introduced to the cathode face 10 of the PCM inthe presence of a catalyst.

A carbonaceous fuel substance from fuel container and delivery assembly4 of the present invention is delivered by optional pump 24 to the anodechamber 18 of the DMFC 3. The fuel mixture passes through channels inassociated flow field plates, and/or a diffusion layers (not shown), andis ultimately presented to the PCM. Catalysts on the membrane surface(or which are otherwise present on the membrane surface) oxidize thecarbonaceous fuel on the catalyzed anode face 8 of the PCM, separatinghydrogen protons and electrons from the fuel and water molecules of thefuel mixture. Upon the closing of a circuit, the protons pass throughPCM 7, which is impermeable to the electrons. The electrons thus seek adifferent path to reunite with the protons, and travel through a load 21of an external circuit, thus providing electrical power to the load. Solong as the reactions continue, a current is maintained through theexternal circuit. Direct oxidation fuel cells produce water (H₂O) andcarbon dioxide (CO₂) which is separated out by gas separator 30, and theun-reacted methanol and water are recirculated to the pump 24. Thecathode effluent is sent to gas separator 32 and water is recirculatedto the pump 24, if desired in a particular application. Those skilled inthe art will recognize that the fuel container and delivery assembly ofthe present invention may also be used in systems with differentarchitectures.

FIG. 2 depicts one illustrative embodiment of the fuel container anddelivery assembly of the present invention. The fuel container anddelivery assembly 200, has an exterior housing that, in the illustrativeembodiment shown, is a substantially rigid cartridge 202. Cartridge 202encloses a collapsible fuel container 204, that may be a flexiblebladder, which is used to hold the liquid fuel for a DMFC or other fuelcell with which it is associated. A plate 206 (which may be formulatedfrom metal or an inert, rigid plastic material) is disposed in contactwith or in close proximity to the flexible bladder 204. The plate 206 isplaced under the force of spring 210. The spring 210 may be a coilspring, as shown in FIG. 2, or may be a “bow” type spring, while stillremaining within the scope of the present invention. The choice ofspring types may also depend upon the form factor and fuel deliveryrequirements of the system.

The plate 206 is, in the illustrative embodiment, of a shape having aperimeter that is substantially the same as the interior profile of theinner wall of the cartridge 202. This increases the likelihood that amaximum even pressure will be applied to the flexible bladder 204because the plate will be stabilized within the cartridge to allow themaximum force of the spring to act at a right angle to the plate 206.The bladder is initially preferably full, containing substantially noair, or other gas. As the liquid fuel is consumed by the DMFC, thebladder will deflate and the compression spring extends to elongate andto continue to apply pressure on the bladder 206, to supply fuel in asubstantially constant flow to the DMFC.

An alternative embodiment is shown in FIG. 3. A cartridge 302, includesa flexible bladder 304 which has a plate 306 disposed next to it. Anexpandable material 310, which may be an elastomer or an expandable foamis disposed within the container contiguous to the plate 306, instead ofa spring, to exert pressure upon the plate 306 which in turn, appliesforce to the bladder 304. In either the embodiment of FIG. 2 or FIG. 3,the pressure-applying element, i.e., either the spring or the expandablematerial, applies sufficient force to the bladder to compress it, thusincreasing the pressure within the bladder to force fluid to flow out ofit, but without rupturing the bladder. The specific pressures willdepend upon the application in which the invention is to be employed andthe materials used, for example.

A conduit 224 (FIG. 2) and conduit 324 (FIG. 3) provide for the flow offuel to the DMFC. In accordance with one illustrative example, theconduit 220 of cartridge 202 is sealed with a seal or plug 224. A needle223 may be used to puncture the seal 224 as well as the flexible bladder204 in order to draw fuel out of the bladder into the DMFC. The needle223 can include a rupture component 2231 to allow for a tear in thebladder when the container is to be disposed of. This allows mixing ofadditives, as previously discussed. Details of this aspect of thedisclosure are described in commonly-owned U.S. Pat. No. 6,460,733,which issued on Oct. 8, 2002, entitled MULTIPLE-WALLED FUEL CONTAINERAND DELIVERY SYSTEM, which is incorporated by reference herein in itsentirety.

A valve located in either the container or within the DMFC system may bedesirable for controlling the flow of fuel as will be understood bythose skilled in the art. It may be further desirable to shape theexternal tank as shown in FIGS. 5A and 5B with sloped sides 76 in orderto funnel fuel into the DMFC.

The valve may be a metering valve as illustrated in FIG. 4. FIG. 4depicts a direct methanol fuel cell system 402 that includes DMFC 403that has fuel supplied to it from a fuel container and delivery assemblyof the present invention 404. In this embodiment of the invention, theDMFC system 402 includes a metering valve 406. The metering valve 406 isactuated by a control system operated in accordance with an instructionset which may be executed by an associated microprocessor or othercontrol logic.

The fuel is released from the fuel container and delivery assembly 404,through the metering valve 406, and released to a pump 424, an internalreservoir or mixing chamber (not shown), into the anode chamber of theDMFC 403. Changes in the concentration of the methanol solution used asthe fuel may be made based upon the information determined fromun-reacted methanol received via anode recirculation loop 410, 420, orfrom information based upon other operating parameters within the fuelcell system. By regulating the concentration of the methanol solution,the problems related to methanol cross over and water carryovertypically addressed in any DMFC, can be controlled, and the DMFC systemmay be able to provide power over a wider power demand profile.

Two additional embodiments of the fuel container and delivery assemblyof the present invention are illustrated in FIGS. 5A and 5B,respectively. In FIG. 5A, the fuel container and delivery assembly 500 aincludes fuel cartridge 502 a. The fuel cartridge 502 a has a fuelcontaining semi-rigid bladder, or envelope, 504 a. In the embodimentillustrated, the bladder may be constructed of two sheets of bladdermaterial that are bonded together, creating an envelope in which thefuel is stored. The envelope tends to collapse as fuel is consumed. Thebladder is placed under pressure by plate 506 a and spring 510 a. Inaddition in the embodiment illustrated in FIG. 5A, it is preferred tofabricate the bladder in such a manner that it has a funnel shape. Inthis manner, the methanol is funneled towards a narrower end proximateto the conduit 524 a at the interface between the fuel container 500 aand the system components leading to the anode side of the fuel cell.

In FIG. 5B, a fuel container and delivery assembly 500 b has a cartridge502 b that houses a bladder 504 b that has a bellows configuration. Thebellows-type bladder is selectively collapsible which avoids portions ofa partially collapsed bag from blocking the flow of methanol, as fuel isconsumed in the operation of the relevant device. As in the otherembodiments described, a plate 506 b is acted upon by a spring 510 b tocompress the bellows-shaped bladder 504 b.

The invention also provides for a simple and accurate fuel gauge to beincluded in the fuel container and delivery assembly. As shown in FIG.6, the fuel container and delivery assembly 600 has an outer container602, that includes a fuel gauge 604 which may be a transparent window,that provide a visual indication of the amount of fuel in the assembly600. The cartridge 602 includes a bladder (not visible in FIG. 6) which,as it is deflated as fuel is consumed, allows the colored plate to movetowards the conduit 624 (and visibly through the window of gauge 604)towards one end of the assembly.

The gauge can be readily calibrated. As the spring elongates, fuel isbeing consumed, and the plate moves towards the conduit end of theassembly. It may be that a portion of the cartridge 602 could becutaway, and a clear material placed in the resulting opening, so thatthe plate (which can be made more visible using coloring and markings)can serve as the gauge. The window 610 of FIG. 6 illustrates thisembodiment, and in the illustration, the fuel cartridge is indicated tobe between one half and three quarters full.

In accordance with another aspect of the invention, thepressure-applying element may be a combination of axial components, suchas the elements 710 a and 710 b in the assembly 700 of FIG. 7. In thisembodiment, the cartridge 702 includes bladder 704. The elements 710 aand 710 b are bow-type springs that act upon plates 712 a and 712 b,respectively. The plates 712 a and 712 b compress the bladder 704. Othertypes of springs, or other elements can be selected for the materials(such as the expandable materials mentioned hereinbefore) for elements710 a and 710 b while remaining within the scope of the presentinvention. This embodiment of the invention may be preferable in certainapplications in order to comply with certain form factors where anarrower device is involved, or in circumstances in which a differentpressure is desired.

FIGS. 8A and 8B illustrate a fuel container and delivery assembly 800having a cartridge 802 that includes a bladder 804. The bladder 804 iscrimped at one end 808 with a displacement sub-assembly 810. Thedisplacement sub-assembly 810 includes a constant force spring 820 thatis wound around an axle 822. The axle 822 moves along a guide to force acompression element 826 against the bladder 804 to force liquid fuel outof the conduit 824. As fuel is released from the bladder, thedisplacement assembly allows that portion of the bladder, which nolonger contains fuel 808 to pass through an opening in the compressionelement 826 (or next to it). Thus, a portion of the bladder thatcontains fuel is maintained under pressure.

A second aspect of this embodiment of the invention includes acompression spring such as the spring 820 (FIG. 8B). The axle and thebladder are mechanically integrated or coupled so that the spring causesthe axle to rotate, minimizing the volume of the bladder. As fuel isreleased through the conduit 824, the axle continues to rotate, andapplies pressure to the bladder 804 causing fuel to be released when anassociated valve is opened.

A locking system can be included in the displacement subassembly, asillustrated in FIG. 9. In accordance with this aspect of the invention,the axle 822, under the action of the constant force spring 820 movesalong a guide 902 that has a serrated track that includes ratchetingteeth 904. The axle 822 fits within the ratcheting teeth 904, and canmove forward along the guide 902, but not backwards in the oppositedirection. This locking system resists the displacement assembly fromslipping back, thus preventing loss of pressure and flow of fuel to thefuel cell.

Alternatively, a cartridge implementing a locking system may be used toprevent the undesired flow of fuel. In this alternate system illustratedin FIGS. 10A and 10B, a cartridge 1000 with a rigid wall 1001 contains afuel bladder 1008, which is fastened or otherwise mechanicallyintegrated to a roller 1010. The roller is fastened to an axle 1012which is also fastened to two transport restriction components 1014 a,1014 b. (FIG. 10B) Attached to the axle is a coil spring 1003, which isalso attached to one transport restriction component (1014 a). Thetorsional action of the coil spring 1003 (FIG. 10C) pulls the assemblyforward, compressing the bladder and decreasing its volume as fuel isdelivered into the system. The pressure applied as the result of thetorsional action of the coil spring can be adjusted by calibrating thespring constant of the coil spring such that it applies enough pressureto ensure that fuel is delivered to the fuel cell system, but does notexceed the valve blocking pressure. Attached to the face of one of thetransport restriction components is a helical spring 1015, which isfastened to the interior aspect of the rigid wall. Collectively, theroller, axle, helical spring and transport restriction components arereferred to as the roller assembly 1016. The roller assembly ispositioned in the cartridge, with the axle either extending through thecartridge, or resting in a groove that is accessible through theexterior wall.

As illustrated in FIG. 10A, integrated or mechanically attached to theinterior aspect of the cartridge are two sets of tracks, each of whichconsists of a smooth track 1004 a,b and a toothed track 1002 a,b. Whenthe cartridge is outside of the DMFC system, the helical spring isextended and presses the roller assembly into the toothed track. Whenforce is applied to the long axis of the axle, the roller assembly isshifted onto the smooth track, where it can be moved forward by the coilspring, thus applying pressure to the fuel bladder as the spring extendsand decreases the volume of the fuel bladder, inducing flow when theassociated valve is opened. When force is released, the roller will bepressed back into the toothed track, where it will be locked in place(FIG. 10D).

Force may be applied via a the insertion process wherein pressure isapplied to the axle by pressing the cartridge into a specially designedopening integrated into the appliance that applies pressure to the axle,thus pushing the transport restriction component onto the smooth track.When the cartridge is removed from the appliance, pressure ceases to beexerted onto the axle, thus allowing the helical spring to push theroller assembly into the toothed track, and preventing it from movingforward. Those skilled in the art will recognize that the functions ofthe springs may be integrated into a single component, or that it may benecessary to use additional springs, depending on the volume of fuelrequired to be moved and the form factors.

Another aspect of the invention is illustrated in FIG. 11. FIG. 11depicts part of a fuel cell system 1100 which has a fuel cell 1101supplied by a fuel container and delivery assembly 1102. The fuelcontainer and delivery assembly has an outer rigid shell 1103 thathouses an inner cartridge 1104. The inner cartridge 1104 encloses acollapsible bag, or flexible bladder 1105, which contains the aqueousfuel solution. As the volume of fuel decreases with fuel consumption,the collapsible bag 1105 accommodates the change in volume. In thisembodiment of the invention, the inner cartridge 1104 is replaceable.The replaceable cartridge 1104 has a fuel outlet conduit (also referredto herein as a fuel exit port) 1106 through which fuel is directed to anoptional pump 1108, to the fuel cell 1101. In addition, the replaceablefuel cartridge 1104 has a fuel return port 1110 to enable therecirculation of unused fuel back into the fuel container 1102. Thisconfiguration enables a relatively low concentration of methanol to beutilized. Once the methanol concentration falls below a useful level,and the useable fuel is consumed, the cartridge can be removed anddisposed of.

In accordance with an alternative aspect of the invention, theembodiment illustrated in FIG. 11 may include a spring 1112 (or otherpressure-applying element such as an expandable foam) to place the fuelunder pressure in such a manner that an initial charge of fuel can bedelivered to the fuel cell without the need of the pump 1108. Inaddition, this initial charge may be used to prime the pump and thuseliminate the need to store the electrical energy needed for the initialpump operation. Once the system is full of fuel, the electrical energyneeded to start the pump can be produced by the fuel cell.

FIG. 12 depicts an alternative embodiment in which a fuel cell system1200, has a fuel cell 1201 (or a plurality of fuel cells) that issupplied with fuel from fuel container and delivery assembly 1202. Inthis embodiment, the fuel container and delivery assembly includes adisposable container 1204 that encloses dual fuel bladders (or bags)1205 a and 1205 b. This enables delivery of different fuelconcentrations to the fuel cell 1201. More specifically, a high methanolconcentration fuel may be delivered from container 1205 a, via fueloutlet 1206 a, through an optional pump 1208 a. A lower methanolconcentration fuel may be delivered from container 1205 b, via the fueloutlet 1206 b, through an optional pump 1208 b. The fuel concentrationcan be controlled by switching between high and lower concentrationfuels. The carbon dioxide gas may be vented at the anode. A feedbackmechanism can be used to control the valve operation depending upon aselected parameter, such as cell temperature, methanol concentration andthe like.

If desired, in an alternative embodiment, the collapsible bags 1205 aand 1205 b may be slightly pressurized by a spring, such as the spring1212, or a gas or compliant, expandable material such as foam. Similarto the embodiment of FIG. 11, the pressure could be used to provide aninitial charge of fuel, to allow for start up of the cell.

It should be understood that the concepts described with respect to eachof the embodiments may be interchanged and varied while remaining withinthe scope of the present invention. Furthermore, it may be beneficial incertain circumstances to fabricate the pressure applying elements sothat the pressure is increased, or decreased, as the fuel is consumed,depending upon the particular application. This may be accomplished byselecting different types of materials. The parameters may also bevaried depending upon the form of the spring that is selected. Inaddition, while the illustrative embodiments have employed compressionsprings that exert force away from the center of the spring, extensionsprings that pull force towards the center of the spring may be employedand the invention is readily adaptable to incorporate such selections.

It is possible to store safety-enhancing additives that add color, odorand flavor to the fuel, or other fluids, as desired in the plenum 212that is defined between the cartridge 202 and the bladder 204 (FIG. 2).Details of the storage of these substances in this manner were set forthin U.S. Pat. No. 6,460,733, which issued on Oct. 8, 2002, entitledMULTIPLE-WALLED FUEL CONTAINER AND DELIVERY SYSTEM, previouslyincorporated by reference herein. As described therein, the containermay also include a rupture component associated with the bladder suchthat the rupture component causes a tear in the bladder such that saidfuel is mixed with the additives upon rupture of the flexible bladder.

FIG. 13 depicts an alternative embodiment in which a fuel cell system1300, has a fuel cell 1301 (or a plurality of fuel cells) that issupplied with fuel from fuel container and delivery assembly 1302. Asnoted, the fuel container and delivery assembly 1302 may be a cartridge,which is inserted into the fuel cell, and when it is empty, it isremoved and replaced with a full cartridge. Alternatively, the fuelcontainer and delivery assembly 1302 may be a type of canister, arefueling device that can be attached to the fuel cell system at anappropriate location to refill an internal fuel reservoir.

In either instance, in accordance with yet another embodiment of theinvention, the fuel container and delivery assembly illustrated in FIG.13 includes a second bladder 1305 b that is provided to receive effluentfrom the cathode and/or anode aspect of the fuel cell 1301, via effluentinlet 1306 b, through an optional pump 1306 b. The effluent may becomprised of carbon dioxide and unreacted fuel and water from the anodeside, or it may be comprised of water from the cathode side, or acombination of both. Inner container 1304 may also enclose each of fuelbladder 1305 a and second bladder 1305 b. The fuel may be delivered frombladder 1305 a, via the fuel outlet 1306 a, through an optional pump1308 a, in the manner hereinbefore described.

If desired, in an alternative embodiment, the collapsible fuel bladder1305 a may be acted upon by an optional force applying element, such asthe spring 1312, or a compliant, expandable material such as foam inorder to provide a continuous fuel delivery, but the effluent bladder1305 b is not under the application of force because the effluent isdesirably entering into the bladder, rather than being expressed fromit. In yet another embodiment (not shown) force applying element 1312 iseliminated from the inventive fuel container, and effluent received fromthe fuel cell(s) in second bladder 1305 b causes second bladder 1305 bto expand, displacing fuel from the fuel bladder 1305 a by delivering itto the fuel cell or fuel cells. The fuel container and delivery assembly1302 could then be detached from the fuel cell system in order todispose of said effluent.

The present invention is not limited to the embodiments illustrated andmay be readily adapted for use with a single bladder, or more than twobladders, or a fuel container and a separate effluent container. Forexample, in an alternative embodiment, the two bladders 1305 a and 1305b may both receive effluent from different parts of the fuel cell oncefuel from fuel bladder 1305 a is delivered to the fuel cell or fuelcells 1301. In such a case the valve and pump 1308 a would be reversibleto facilitate the removal of fluids from the fuel cell system. In thatcase, the fuel delivery cartridge or canister could be detached from thefuel cell system once the fuel was delivered and effluent or othersubstances are received from the fuel cell system.

It should be understood that the present invention provides a convenientand useful solution for safely disposing of waste products of the fuelcell, or other substances, which might be otherwise difficult toeliminate.

As stated, it should also be understood that the present invention canalso be readily employed with fuels other than methanol ormethanol/water mixtures.

The foregoing description has been directed to specific embodiments ofthe invention. It will be apparent, however, that other variations andmodifications may be made to the described embodiments, with theattainment of some or all of the advantages of such. Therefore, it isthe object of the appended claims to cover all such variations andmodifications as come within the true spirit and scope of the invention.

1. A method for delivering fuel to and removing effluent from a fuelcell in a fuel cell system, comprising: (A) providing a direct oxidationfuel cell including a membrane electrode assembly; (B) coupling acontainer with said fuel cell, including: (i) providing within saidcontainer, a first inner bladder being substantially fully expanded uponbeing filled with liquid fuel, and having a fuel outlet conduit tosupply liquid fuel to said direct oxidation fuel cell; and (ii)providing within said container, a second inner bladder for receivingeffluent from said fuel cell through an effluent inlet leading from saidfuel cell into said container as reactions occur in said fuel cell, insuch a manner that as effluent enters said second inner bladder, saidsecond inner bladder expands and contacts said first inner bladder todisplace fuel out of said first inner bladder to said fuel cell, whereinthe second inner bladder is not under application of force.
 2. Themethod of claim 1, further comprising: disposing said first and secondbladders in a rigid outer shell.
 3. The method of claim 2, furthercomprising: providing said second inner bladder as a removable element,and detaching and removing said second inner bladder to disposed of saideffluent.
 4. The method of claim 3, further comprising: receiving othersubstances into said second inner bladder in addition to or instead ofeffluent from said fuel cell.
 5. A method for delivering fuel to andremoving effluent from a direct oxidation fuel cell in a fuel cellsystem, comprising: (A) providing the direct oxidation fuel cellincluding a membrane electrode assembly; (B) coupling a fuel containerto the fuel cell, wherein the fuel container has a first inner bladderbeing substantially fully expanded upon being filled with liquid fuel,and having a fuel outlet conduit to supply liquid fuel to the directoxidation fuel cell, and a second inner bladder for receiving effluentfrom the fuel cell through an effluent inlet leading from the fuel cellinto the fuel container as reactions occur in said fuel cell, in such amanner that as effluent enters the second inner bladder, the secondinner bladder expands and contacts the first inner bladder displacingfuel out of the first inner bladder to the fuel cell, wherein the firstand second inner bladder are not under application of force from a forceapplying element.
 6. The method of claim 5, further comprising: pumpingthe effluent out of the fuel cell to the second bladder.
 7. The methodof claim 5, further comprising: disposing the first and second bladdersin a rigid outer shell.
 8. The method of claim 7, further comprising:providing the second inner bladder as a removable element, and detachingand removing the second inner bladder to dispose of the effluent.
 9. Themethod of claim 5, further comprising: receiving other substances intosaid second inner bladder in addition to or instead of effluent from thefuel cell.